Fellow builders:
I've gotten to the point of getting ready to mix and pour the insulating layer of Perlite and Portland cement. I opened the bag of perlite for the first time and found that is sand like in consistency. Is that too fine to mix with Portland and pour? Should I junk the stuff and buy something else. Vermiculite in quantity seems to be tough to find here in Austin

Thanks

Neil2

07-22-2009 08:12 PM

Re: Perlite Question

I think that that is too fine. Look for a coarser grain - something like 1/8 inch or better particles.

RTflorida

07-22-2009 09:50 PM

Re: Perlite Question

Sounds a bit too fine to me, as well. I used Vermiculite for the insulation slab - was labeled "medium grade" and until I reached the bottom 25% of each bag it was fine. The bottom of each bag was like brown talcum powder (a lot of settling), needless to say, I wasn't thrilled with the waste.

I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.

The bottom line - I think you need it a bit courser, makes the mix more "airy" and adds to the insulation value (my opinion).

RT

charger10s

07-22-2009 09:58 PM

Re: Perlite Question

Quote:

Originally Posted by RTflorida
(Post 60237)

...

I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.
....
RT

RT, can you tell us the website where you bought your perlite?

Thanks!

Big Tone

07-25-2009 01:56 AM

Re: Perlite Question

Re Perlite question:
Thanks, Neil, Florida. I am worried about this question of vermiculite grade/size. Is there an official view? It isn't mentioned in the instructions as you probably know (and sorry, I am not familiar with Grape Nuts cereal coming from Australia). Size of rice grains? A pea? Big as the end of your thumb? I bought one bag (vermiculite grade 1) and it's just a bit bigger than coarse sand, so I guess that's no good. Help!

Gromit

07-25-2009 06:02 AM

Re: Perlite Question

1 Attachment(s)

Neither grape nor nut.

DimTex

07-25-2009 10:15 AM

Re: Perlite Question

I found my perlite at a hydroponics store, they had all grades from fine to coarse and the price was very reasonable

blacknoir

07-25-2009 11:15 AM

Re: Perlite Question

Only kind I've found so far was Miracle-Gro and it's not cheap.. if someone has an online source please post it!

DimTex

07-25-2009 11:22 AM

Re: Perlite Question

I found perlite in bulk at a local hydroponics store, and at a good price